As the planet's population increases, pollution entering waterways increases, and the availability of non-renewable raw resource materials reduces. It is possible to reduce this pollution by constructing treatment wetlands, but these wetlands use significant amounts of natural aggregates. The question arises: is it not possible to replace non-renewable resources with recycled materials made from construction and demolition waste? This article examines the applicability of recycled building materials as filter media for vertical subsurface flow filters. The recycled aggregates of the 0-4 mm fraction are evaluated in terms of grain size and hydraulic conductivity. For the Czech Republic's available raw recycled aggregates, washing methods are proposed to produce materials that meet the required grain size limits. Untreated aggregates contain a significant proportion of particles smaller than 0.063 mm (up to 21.8%), significantly reducing their hydraulic conductivity and preventing their use in water filtration. However, concrete and masonry aggregates with dust particle contents of 0.3% and 1.5% can be obtained through washing. The washed materials subsequently show an increase in hydraulic conductivity up to the required range of values, that is 10-4-10-3 m s-1. According to the evaluation carried out, it is possible to apply treated recycled materials to wastewater filtration. At the same time, the application of construction waste in constructed treatment wetlands creates opportunities to use fine recycled aggregates (0-4 mm) in these areas, which are currently limited, in the future. [ABSTRACT FROM AUTHOR]